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    <script>
        // 1.   声明一个函数实现如下效果：[‘a’,‘a’,‘a’,‘b’,‘b’,‘c’,‘c’,‘c’,‘c’,‘d’,‘d’,‘d’,‘d’] —> { a: 3, b: 2, c: 4, d: 4 }

        let arr = ['a', 'a', 'a', 'b', 'b', 'c', 'c', 'c', 'c', 'd', 'd', 'd', 'd']



        function lengthRepeat(arr) {
            let obj = {}


            for (let i = 0; i < arr.length; i++) {

                obj[arr[i]] = obj[arr[i]] +1 || 1
            }
            return obj
        }

        console.log(lengthRepeat(arr));
    </script>
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